Effect of particle size on thermal decomposition and devolatilization kinetics of melon seed shell

Thermogravimetric analysis (TGA) and devolatilization kinetics of melon seed shell (MSS) at different particle sizes (150 mu m and 500 mu m) and at different heating rates (10, 15, 20, and 25 degrees C/min) were investigated with the aid of TGA. The results of the TGA analysis show that the TGA curves corresponding to the first and third stages for 150 mu m particle sizes exhibited some bumps that developed at the first and third stages of pyrolysis. It was also observed that at constant heating rate, the maximum peak temperature increases as the particle sizes increase from 150 to 500 mu m, whereas 500 mu m particle sizes exhibited higher peak temperatures compared to 150 mu m particle sizes. The resulting TGA data were applied to the Kissinger (K), Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods and kinetic parameters (activation energy, E and frequency factor, A) were determined. The E and A obtained using K method were 74.27kJ mol(-1) and 3.84x10(5)min(-1) for 150 mu m particle size, whereas for 500 mu m particle size were 97.12kJ mol(-1) and 3.74x10(7)min(-1), respectively. However, the average E and A obtained using KAS and FWO methods were 82.35kJ mol(-1), 1.29x10(7)min(-1), and 88.50kJ mol(-1), 1.32x10(7)min(-1) for 150 mu m particle sizes. While for 500 mu m particle sizes, the E and A were 108.46kJ mol(-1), 3.14x10(9)min(-1), and 113.05kJ mol(-1), 7.56x10(9)min(-1), respectively. It was observed that E and A calculated from FWO and KAS methods were very close and higher than that obtained by K method. It was observed that the minimum heat required for the cracking of MSS particles into products is reached later at higher peak temperatures since the heat transfer is less effective as they are at lower peak temperatures.